package com.test;

import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

/**
 * Hello world!
 *
 */
public class App 
{
    public static void main( String[] args )
    {
        List<String> entries = new ArrayList<String>();
        entries.add("aa");
        entries.add("bb");
        entries.add("cc");


        Map<String, String> x = new ConcurrentHashMap<String, String>();

        x.put(null, "a");
    }
}